The p400/Brd8 Chromatin Remodeling Complex Promotes Adipogenesis by Incorporating Histone Variant H2A.Z at PPARγ Target Genes

Abstract

Adipogenesis, the biological process by which preadipocytes differentiate into mature fat cells, is coordinated by a tightly regulated gene expression program. Indeed, it has been reported that a large number of genetic events, from fat cell-specific transcription factors expression, such as the master regulator of fat cell differentiation peroxisome proliferator-activated receptor (PPAR)γ2 to epigenetic modifications, govern the acquisition of a mature adipocyte phenotype. Here, we provide evidence that the E1A-binding protein p400 (p400) complex subunit bromo-containing protein 8 (Brd8) plays an important role in the regulation of PPARγ target genes during adipogenesis by targeting and incorporating the histone variant H2A.Z in transcriptional regulatory regions. The results reported here indicate that expression of both Brd8 and p400 increases during fat cell differentiation. In addition, small hairpin RNA-mediated knockdown of Brd8 or H2A.Z completely abrogated the ability of 3T3-L1 preadipocyte to differentiate into mature adipocyte, as evidenced by a lack of lipid accumulation. Chromatin immunoprecipitation experiments also revealed that the knockdown of Brd8 blocked the accumulation of PPARγ, p400, and RNA polymerase II and prevented the incorporation of H2A.Z at two PPARγ target genes. Taken together, these results indicate that the incorporation of the histone variant H2A.Z at the promoter regions of PPARγ target genes by p400/Brd8 is essential to allow fat cell differentiation.

Murine and Human Spermatids Are Characterized by Numerous, Newly Synthesized and Differentially Expressed Transcription Factors and Bromodomain-Containing Proteins

“…BRDT is the best-characterized bromodomain-containing protein in spermatogenesis; it is involved in gene regulation processes and later in the histone-to-protamine transition [17,55]. The function of BRD8 has been hardly described, but it seems to be required for the incorporation of the histone variant H2A.Z and gene activation during adipogenesis [56]. In human spermatids, the presence of BRD8 and BRDT overlaps with that of both active RNA polymerase II and TNP1 (Fig.…”

Early adipogenesis is regulated through USP7-mediated deubiquitination of the histone acetyltransferase TIP60

“…By deubiquitinating the transcription factor REST, USP7 plays a critical role in the maintenance of neural progenitor cells 46 . Whereas these studies indicate that Tip60 and/ or USP7 are important to maintain cells in an undifferentiated state, the differentiation of 3T3-L1 adipocytes and human primary adipocytes critically depends on Tip60 (refs 17,47), on the Brd8 and p400 proteins, which are also part of the NuA4/ Tip60 complex 18 , and on USP7 (current study). Taken together, current evidence therefore suggests that Tip60 and USP7 can both inhibit and stimulate proliferation, apoptosis and differentiation, depending on the cellular context.…”

“…Finally, our transcriptome analysis revealed very few 'late' adipocyte genes to be critically regulated by Tip60 and/or USP7 (Fig. 4b), despite the fact that Tip60 is recruited to the Fabp4, Plin1 (Perilipin) and Pparg promoters in mature 3T3-L1 adipocytes 17,18 . Taken together, these findings suggest that the critical role of Tip60-USP7 adipogenesis may be the regulation of MCE (days 0-2), whereas these proteins may be redundant for the maintenance of the adipogenic phenotype.…”

“…Recently, we found Tip60 to be essential for the differentiation of 3T3-L1 adipocytes 17 . As Tip60 protein levels, but not mRNA levels, are upregulated during adipogenesis 17,18 , and as Tip60 can be degraded by the proteasome 16,19 , these findings suggest that the Tip60 protein may be stabilized through deubiquitination during adipogenesis.…”

The chromatin remodeling protein INO80 contributes to the removal of H2A.Z at the p53‐binding site of the p21 gene in response to doxorubicin

“…The yeast Swr1 chromatin remodeling complex and its two homologs in human SRCAP and p400/TIP60 complexes incorporate H2A.Z into nucleosomes [8][9][10] and H2A.Z deposition at specific loci in chromatin is often affected by histone modification. The yeast Swr1 chromatin remodeling complex and its two homologs in human SRCAP and p400/TIP60 complexes incorporate H2A.Z into nucleosomes [8][9][10] and H2A.Z deposition at specific loci in chromatin is often affected by histone modification.…”